Loans Receivable and Allowance for Credit Losses (Aging Analysis on Non-PCI Loans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Nonaccrual and Past Due Loans
Number of days beyond loan classified nonaccrual	90 days
Total loans	$ 28,975,718	$ 25,503,139
Commercial Lending
Nonaccrual and Past Due Loans
Total loans	22,210,001	19,917,365
Commercial Lending | C&I
Nonaccrual and Past Due Loans
Total loans	10,697,231	9,640,563
Commercial Lending | CRE
Nonaccrual and Past Due Loans
Total loans	8,936,897	8,016,109
Commercial Lending | Residential loan | Multifamily
Nonaccrual and Past Due Loans
Total loans	1,916,176	1,585,939
Commercial Lending | Construction and land
Nonaccrual and Past Due Loans
Total loans	659,697	674,754
Consumer Lending
Nonaccrual and Past Due Loans
Total loans	6,765,717	5,585,774
Consumer Lending | Residential loan | Single-family
Nonaccrual and Past Due Loans
Total loans	4,646,289	3,509,779
Consumer Lending | HELOCs
Nonaccrual and Past Due Loans
Total loans	1,782,924	1,760,776
Consumer Lending | Other consumer
Nonaccrual and Past Due Loans
Total loans	336,504	315,219
Non-PCI impaired loans
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	67,677	101,189
Total Nonaccrual Loans	114,309	122,817
Current Accruing Loans	28,311,445	24,636,688
Total loans	28,493,431	24,860,694
Non-PCI impaired loans | Commercial Lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	40,544	76,963
Total Nonaccrual Loans	101,889	116,473
Current Accruing Loans	21,716,666	19,239,522
Total loans	21,859,099	19,432,958
Non-PCI impaired loans | Commercial Lending | C&I
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	31,046	47,331
Total Nonaccrual Loans	69,213	81,256
Current Accruing Loans	10,585,177	9,473,589
Total loans	10,685,436	9,602,176
Non-PCI impaired loans | Commercial Lending | CRE
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	3,880	20,313
Total Nonaccrual Loans	26,986	26,907
Current Accruing Loans	8,628,343	7,620,441
Total loans	8,659,209	7,667,661
Non-PCI impaired loans | Commercial Lending | Residential loan | Multifamily
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	4,860	4,325
Total Nonaccrual Loans	1,717	2,984
Current Accruing Loans	1,848,551	1,482,976
Total loans	1,855,128	1,490,285
Non-PCI impaired loans | Commercial Lending | Construction and land
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	758	4,994
Total Nonaccrual Loans	3,973	5,326
Current Accruing Loans	654,595	662,516
Total loans	659,326	672,836
Non-PCI impaired loans | Consumer Lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	27,133	24,226
Total Nonaccrual Loans	12,420	6,344
Current Accruing Loans	6,594,779	5,397,166
Total loans	6,634,332	5,427,736
Non-PCI impaired loans | Consumer Lending | Residential loan | Single-family
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	18,624	17,671
Total Nonaccrual Loans	5,923	4,214
Current Accruing Loans	4,504,364	3,348,784
Total loans	4,528,911	3,370,669
Non-PCI impaired loans | Consumer Lending | HELOCs
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	8,472	5,451
Total Nonaccrual Loans	4,006	2,130
Current Accruing Loans	1,756,439	1,734,271
Total loans	1,768,917	1,741,852
Non-PCI impaired loans | Consumer Lending | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	37	1,104
Total Nonaccrual Loans	2,491	0
Current Accruing Loans	333,976	314,111
Total loans	336,504	315,215
Non-PCI impaired loans | Accruing Loans 30-59 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	57,551	73,152
Non-PCI impaired loans | Accruing Loans 30-59 Days Past Due | Commercial Lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	39,982	60,230
Non-PCI impaired loans | Accruing Loans 30-59 Days Past Due | Commercial Lending | C&I
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	30,964	45,052
Non-PCI impaired loans | Accruing Loans 30-59 Days Past Due | Commercial Lending | CRE
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	3,414	6,233
Non-PCI impaired loans | Accruing Loans 30-59 Days Past Due | Commercial Lending | Residential loan | Multifamily
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	4,846	3,951
Non-PCI impaired loans | Accruing Loans 30-59 Days Past Due | Commercial Lending | Construction and land
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	758	4,994
Non-PCI impaired loans | Accruing Loans 30-59 Days Past Due | Consumer Lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	17,569	12,922
Non-PCI impaired loans | Accruing Loans 30-59 Days Past Due | Consumer Lending | Residential loan | Single-family
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	13,269	9,595
Non-PCI impaired loans | Accruing Loans 30-59 Days Past Due | Consumer Lending | HELOCs
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	4,286	2,845
Non-PCI impaired loans | Accruing Loans 30-59 Days Past Due | Consumer Lending | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	14	482
Non-PCI impaired loans | Accruing Loans 60-89 Days Past Due
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	10,126	28,037
Non-PCI impaired loans | Accruing Loans 60-89 Days Past Due | Commercial Lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	562	16,733
Non-PCI impaired loans | Accruing Loans 60-89 Days Past Due | Commercial Lending | C&I
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	82	2,279
Non-PCI impaired loans | Accruing Loans 60-89 Days Past Due | Commercial Lending | CRE
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	466	14,080
Non-PCI impaired loans | Accruing Loans 60-89 Days Past Due | Commercial Lending | Residential loan | Multifamily
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	14	374
Non-PCI impaired loans | Accruing Loans 60-89 Days Past Due | Commercial Lending | Construction and land
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	0	0
Non-PCI impaired loans | Accruing Loans 60-89 Days Past Due | Consumer Lending
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	9,564	11,304
Non-PCI impaired loans | Accruing Loans 60-89 Days Past Due | Consumer Lending | Residential loan | Single-family
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	5,355	8,076
Non-PCI impaired loans | Accruing Loans 60-89 Days Past Due | Consumer Lending | HELOCs
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	4,186	2,606
Non-PCI impaired loans | Accruing Loans 60-89 Days Past Due | Consumer Lending | Other consumer
Nonaccrual and Past Due Loans
Total Accruing Past Due Loans	23	622
Non-PCI impaired loans | Nonaccrual Loans Less Than 90 Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	34,351	78,779
Non-PCI impaired loans | Nonaccrual Loans Less Than 90 Days Past Due | Commercial Lending
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	34,256	78,614
Non-PCI impaired loans | Nonaccrual Loans Less Than 90 Days Past Due | Commercial Lending | C&I
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	27,408	60,519
Non-PCI impaired loans | Nonaccrual Loans Less Than 90 Days Past Due | Commercial Lending | CRE
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	5,430	14,872
Non-PCI impaired loans | Nonaccrual Loans Less Than 90 Days Past Due | Commercial Lending | Residential loan | Multifamily
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	1,418	2,790
Non-PCI impaired loans | Nonaccrual Loans Less Than 90 Days Past Due | Commercial Lending | Construction and land
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	0	433
Non-PCI impaired loans | Nonaccrual Loans Less Than 90 Days Past Due | Consumer Lending
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	95	165
Non-PCI impaired loans | Nonaccrual Loans Less Than 90 Days Past Due | Consumer Lending | Residential loan | Single-family
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	6	0
Non-PCI impaired loans | Nonaccrual Loans Less Than 90 Days Past Due | Consumer Lending | HELOCs
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	89	165
Non-PCI impaired loans | Nonaccrual Loans Less Than 90 Days Past Due | Consumer Lending | Other consumer
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	0	0
Non-PCI impaired loans | Nonaccrual Loans 90 or More Days Past Due
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	79,958	44,038
Non-PCI impaired loans | Nonaccrual Loans 90 or More Days Past Due | Commercial Lending
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	67,633	37,859
Non-PCI impaired loans | Nonaccrual Loans 90 or More Days Past Due | Commercial Lending | C&I
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	41,805	20,737
Non-PCI impaired loans | Nonaccrual Loans 90 or More Days Past Due | Commercial Lending | CRE
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	21,556	12,035
Non-PCI impaired loans | Nonaccrual Loans 90 or More Days Past Due | Commercial Lending | Residential loan | Multifamily
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	299	194
Non-PCI impaired loans | Nonaccrual Loans 90 or More Days Past Due | Commercial Lending | Construction and land
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	3,973	4,893
Non-PCI impaired loans | Nonaccrual Loans 90 or More Days Past Due | Consumer Lending
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	12,325	6,179
Non-PCI impaired loans | Nonaccrual Loans 90 or More Days Past Due | Consumer Lending | Residential loan | Single-family
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	5,917	4,214
Non-PCI impaired loans | Nonaccrual Loans 90 or More Days Past Due | Consumer Lending | HELOCs
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	3,917	1,965
Non-PCI impaired loans | Nonaccrual Loans 90 or More Days Past Due | Consumer Lending | Other consumer
Nonaccrual and Past Due Loans
Total Nonaccrual Loans	$ 2,491	$ 0